Targeted for the closest look at Io, Voyager 1 flew the more hazardous course, passing between Jupiter and Io, where the radiation environment is the most intense. Voyager 2’s flight path gave Jupiter and its intense radiation a much wider berth. Unlike Voyager 1, which encountered the five innermost satellites as it was leaving Jupiter, Voyager 2 encountered the satellites as it was approaching the planet, thus providing closeup photography of opposite sides of the satellites.
March 5, 1979. Voyager 1’s unique flight path allowed scientists to study at close range 5 of Jupiter’s 13 known satellites. Each is shown at its closest point to the trajectory of Voyager 1’s outbound flight away from Jupiter. Closest approach was 280,000 kilometers (174,000 miles) from Jupiter.
July 9, 1979. Voyager 2’s closest approach to Jupiter was 645,000 kilometers (400,000 miles) from the planet. Voyager 2 encountered the satellites on its inbound journey to Jupiter, which enabled the spacecraft to photograph the opposite sides of the satellites.
Arriving at Jupiter from slightly different angles, both spacecraft measured the large, doughnut-shaped ring of charged sulfur and oxygen ions, called a torus, encircling the planet at about the orbit of Io. Then, both spacecraft disappeared behind Jupiter, out of view of Earth and Sun, for about two hours. During this time, measurements were taken on the planet’s dark side. Each spacecraft took over 15,000 photographs of Jupiter and its satellites.
Voyager spacecraft and scientific instruments.
From the moment of launch, the Voyager spacecraft have been monitored by a worldwide tracking system of nine giant antennas strategically located around the world in California, Spain, and Australia to ensure constant radio contact with the spacecraft as the Earth rotates. Radio contact with Voyagers 1 and 2 has not been instantaneous, however. When Voyager 1 flew past Jupiter, radio signals between Earth and the spacecraft took 37 minutes; when Voyager 2 arrived, the signals took 52 minutes because by then the planet was farther from Earth.
The pictures in this book were taken by a shuttered television-type camera. Each picture is composed of 640,000 dots, which were converted into binary numbers before being radioed to Earth. When the signals reached Earth, they were reconverted by computer into dots and reassembled into the original image. Most of the color pictures are composed of three images, each one taken through a different color filter: blue, orange, or green. The images were combined and the original color was reconstructed by computer. The computer eliminated many of the imperfections that crept into the images, and enhanced some of the images by emphasizing different colors.